Vaporizers are used in numerous households in the country. They are inexpensive and reliable. However, as the hardness of the water varies from one locality to the next, so does its conductivity and the rate of vaporization. If the water is too hard, the electric current is too high, and the vaporizer malfunctions. The symptoms of this malfunction include premature depletion of the water reservoir, and spraying of hot liquid water from the steam outlet. The remedy currently recommended by manufacturers is dilution of the local tap water with distilled water, which reduces the conductivity. This solution is inconvenient and expensive.
The above problem has been known for a long time and several patents have been granted for solutions. Many patents propose to increase the current path between the electrodes of the vaporizer in order to increase the total resistance between them and thus to reduce the vaporization rate. In U.S. Pat. Nos. 3,308,267 to Fenstennaker, and 4,205,222 to Williams, and also in Canadian patent 1,166,296 to Howard-Leicester, it is suggested that the current path be lengthened by interposing plastic insulating components between the electrodes. In the most sophisticated of these three patents, Williams proposes to equip his boiler with a movable insulating sleeve 17, interposed between electrode 8 and counter-electrode 10, in order to vary the current path, as shown in FIG. 1 of the patent.
No doubt, each of the proposed solutions will work in the environment for which the device is designed, but none of them responds to the needs of a typical household user. The Williams apparatus, for instance, is much too complicated and expensive. The Fenstermaker vaporizer is simple and inexpensive, but it can not easily be adjusted to the needs of the individual user. His insulating strip 23, which lengthens the current path between electrodes 20 and 21, is permanently fixed to electrode 21 at the factory.